Fixed PHP memory leaks and arginfo errors (#8614)

* Fixed a bunch of incorrect arginfo and a few incorrect error messages.

* Passes mem check test with no leaks!

* WIP.

* Fix build warning that was causing Bazel build to fail.

* Added compatibility code for PHP <8.0.

* Added test_valgrind target and made tests Valgrind-clean.

* Updated Valgrind test to fail if memory leaks are detected.

* Removed intermediate shell script so commands are easier to cut, paste, and modify.

* Passing all Valgrind tests!

* Hoist addref into ObjCache_Get().

* Removed special case of map descriptors by keying object map on upb_msgdef.

* Removed all remaining RETURN_ZVAL() macros.

* Removed all explicit reference add/del operations.

* Added REFCOUNTING.md to Makefile.am.
diff --git a/kokoro/linux/php_all/build.sh b/kokoro/linux/php_all/build.sh
index ba269e5..1ee79ad 100755
--- a/kokoro/linux/php_all/build.sh
+++ b/kokoro/linux/php_all/build.sh
@@ -5,13 +5,16 @@
 
 set -ex
 
-cd $(dirname $0)
+# Change to repo base.
+cd $(dirname $0)/../../..
+
+docker run $(test -t 0 && echo "-it") -v$PWD:/workspace gcr.io/protobuf-build/php/linux:8.0.5-dbg-14a06550010c0649bf69b6c9b803c1ca609bbb6d "composer test_valgrind"
+
+docker run $(test -t 0 && echo "-it") -v$PWD:/workspace gcr.io/protobuf-build/php/linux:7.0.33-dbg-14a06550010c0649bf69b6c9b803c1ca609bbb6d "composer test && composer test_c"
+docker run $(test -t 0 && echo "-it") -v$PWD:/workspace gcr.io/protobuf-build/php/linux:7.3.28-dbg-14a06550010c0649bf69b6c9b803c1ca609bbb6d "composer test && composer test_c"
+docker run $(test -t 0 && echo "-it") -v$PWD:/workspace gcr.io/protobuf-build/php/linux:7.4.18-dbg-14a06550010c0649bf69b6c9b803c1ca609bbb6d "composer test && composer test_c"
+docker run $(test -t 0 && echo "-it") -v$PWD:/workspace gcr.io/protobuf-build/php/linux:8.0.5-dbg-14a06550010c0649bf69b6c9b803c1ca609bbb6d "composer test && composer test_c"
 
 # Most of our tests use a debug build of PHP, but we do one build against an opt
 # php just in case that surfaces anything unexpected.
-../test_php.sh gcr.io/protobuf-build/php/linux:8.0.5-14a06550010c0649bf69b6c9b803c1ca609bbb6d
-
-../test_php.sh gcr.io/protobuf-build/php/linux:7.0.33-dbg-14a06550010c0649bf69b6c9b803c1ca609bbb6d
-../test_php.sh gcr.io/protobuf-build/php/linux:7.3.28-dbg-14a06550010c0649bf69b6c9b803c1ca609bbb6d
-../test_php.sh gcr.io/protobuf-build/php/linux:7.4.18-dbg-14a06550010c0649bf69b6c9b803c1ca609bbb6d
-../test_php.sh gcr.io/protobuf-build/php/linux:8.0.5-dbg-14a06550010c0649bf69b6c9b803c1ca609bbb6d
+docker run $(test -t 0 && echo "-it") -v$PWD:/workspace gcr.io/protobuf-build/php/linux:8.0.5-14a06550010c0649bf69b6c9b803c1ca609bbb6d "composer test && composer test_c"